Fix gimbal indicator pitch value jitter

[DonLakeFlyer]

Values would bounce between 0.0 and -0.0 and -90 and nan.

[DonLakeFlyer]

@Davidsastresas Can you test this out?

[Copilot]

Pull request overview

This pull request fixes gimbal indicator pitch value jitter where values would bounce between 0.0 and -0.0, and also handles NaN values that occurred at boundary conditions (e.g., -90 degrees pitch). The fix involves three coordinated changes: improving quaternion-to-Euler conversion to avoid NaN values, stripping negative zero from floating-point string representations, and using the Fact System's built-in string formatting in the UI.

Key changes:

• Replaced mavlink_quaternion_to_euler with QQuaternion::toEulerAngles() for more robust boundary condition handling
• Added negative zero stripping to the Fact System's string conversion to prevent -0.0 display jitter
• Updated UI to use valueString property instead of manual toFixed() formatting

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
src/UI/toolbar/GimbalIndicator.qml	Changed gimbal angle displays to use Fact's valueString property instead of rawValue.toFixed(1), leveraging built-in NaN handling and formatting
src/Gimbal/GimbalController.cc	Replaced MAVLink quaternion conversion with Qt's QQuaternion::toEulerAngles() which returns degrees and handles boundary conditions better, preventing NaN values
src/FactSystem/Fact.cc	Added stripNegativeZero lambda to convert -0.0 and -0 to positive zero in float/double string representations, eliminating display jitter

[Davidsastresas]

I just tested, it looks good to me. Thank you for keeping me in the loop.

I had a weird crash going to the joystick menu and disconnecting the joystick, in Linux. However I wasn't able to reproduce it after several tries.

[DonLakeFlyer]

Thanks for testing David